Grant Skinner has just released the source code for his pathfinding class. The algorithm is not the normal A*, but his own flavour which is speed optimized for flash - as a tradeoff it might fail sometimes for long paths. But, as Grant states it's "Fast enough to use with multiple enemies/characters in real time, and accurate enough to be useful."

You will find it in the laboratory section of gskinner.com (would be a nice idea to be able to link to items directly, Grant...)